1. Field of the Invention
The present invention relates to a stereoscopic image display apparatus, and more particularly to such apparatus adapted for stereoscopic image display in a television, a video display, a computer monitor, a game machine or the like.
2. Related Background Art
As the conventional stereoscopic image display apparatus, there is known an apparatus of a system of polarizing glasses. In this system, the image display device is provided with a liquid crystal shutter for obtaining different polarized states for a right-eye parallax image R and a left-eye parallax image L. The polarized state is switched in synchronization with the field signal of the displayed image and the observer wearing polarizing glasses observes such switched display, whereby the stereoscopic observation is realized by splitting the left and right images to the respective eyes in time-sequential manner. However such system is cumbersome for the user, being required to always wear the polarizing glasses.
On the other hand, among the stereoscopic image display apparatus not using such polarizing glasses, there is known a system providing a lenticular lens in front of the display device, thereby spatially separating the images for the left and right eyes. FIGS. 1A and 1B are schematic views showing such conventional system with the lenticular lens, and are respectively a cross-sectional view seen from above the observer and a front view of display pixels of the liquid crystal display.
In these drawings, 501 indicates a display pixel portion of a liquid crystal display device, of which glass substrate, color filter, electrodes, polarizing filters, rear light source etc. are omitted from the illustration. The display pixel portion 501 is composed of apertures 502 having color filters and constituting pixels, and a black matrix 503 separating such pixels. The liquid crystal display is provided thereon, at the side of the observer, with a lenticular lens 504 consisting of cylindrical lenses having a semicircular cross section as illustrated and extending perpendicularly to the plane of drawing, and the display pixel portion 501 of the liquid crystal display is positioned at the focal plane of such lenticular lens.
In the display pixel portion 501, stripe-shaped pixels Ri for the right eye and stripe-shaped pixels Li for the left eye are alternately displayed in such a manner that each pair of such pixels corresponds to a pitch of the lenticular lens, whereby such paired pixels are optically separated and respectively focused on the right eye ER and the left eye EL of the observer by means of the lenticular lens 504o thereby enabling stereoscopic observation.
In FIGS. 1A and 1B there are shown spatial areas where the stripe pixels for the right and left eyes can be respectively viewed by the cylindrical lens 504 at the central portion of the display. Also for other cylindrical lenses of the lenticular lens, similarly separated spatial areas overlap at the right and left eyes of the observer. Thus the stripe pixels for the right eye and those for the left eye can be uniformly separated and observed over the entire image, and parallax images R and L, each consisting of a group of stripe pixels, can be respectively observed by the right eye and the left eye.
In this system, the two parallax images R, L are respectively divided into vertical stripe-shaped pixels, which are alternately arranged from the left or right end of the image area as a single striped image for display on the display pixel portion 501, so that the resolution of the image display device is inevitably reduced to xc2xd.
On the other hand, the Japanese Patent Laid-open Application Nos. 5-107663 and 7-234459 disclose stereoscopic image display apparatus of the lenticular system without such reduction in the resolution.
FIGS. 2A, 2B and 2C are views showing the basic configuration of the stereoscopic image display apparatus disclosed in the Japanese Patent Laid-open Application No. 5-107663. This stereoscopic image display apparatus is composed of a light direction switching device 601 consisting of a planar matrix light source 602 and a lenticular sheet 603, and a transmissive display device 604. The planar matrix light source 602 is provided, within the width of a lenticular lens constituting the lenticular sheet 603, with a stripe-shaped light source for the right eye (a column marked with xe2x80x9cRxe2x80x9d of 602R in FIG. 2B) and a stripe-shaped light source for the left eye (a column marked with xe2x80x9cLxe2x80x9d of 602L in FIG. 2B) as a pair.
This display apparatus functions in the following manner. When the stripe-shaped light source for the right eye (602R in FIG. 2B) is turned on to emit the illuminating light from the entire area of the lenticular sheet to the area for the right eye, a parallax image for the right eye (604R in FIG. 2C) is displayed in an odd-numbered frame in synchronization, and, when the stripe-shaped light source for the left eye (602L in FIG. 2B) is turned on to emit the illuminating light from the entire area of the lenticular sheet to the area for the left eye, a parallax image for the left eye (604L in FIG. 2C) is displayed in an even-numbered frame in synchronization. Thus the parallax image R and L need not be divided into stripe pixels but can be displayed entirely in the even and odd frames, so that the stereoscopic image display device can be realized without the loss of the resolution.
The conventional stereoscopic image display apparatus of the lenticular lens system shown in FIGS. 1A and 1B, having the lenticular lens on the liquid crystal display at the observer side thereof, is associated with drawbacks that the image quality is deteriorated by the surface reflection of the lenticular lens and that Moire fringes are formed by the black matrix of the liquid crystal display.
The conventional stereoscopic image display apparatus shown in FIGS. 2A, 2B and 2C realizes the stereoscopic view by time-divided display of the right-eye parallax image R and the left-eye parallax image L, but the image switching has to be made at a high speed in order to avoid flickering phenomenon.
Isono et al. (xe2x80x9cCondition for time-divided stereoscopic viewxe2x80x9d, J. of Television Association, Vol.41, No.6(1987), pp549-555) reported that the stereoscopic view could not be achieved in the time-divided display of a field frequency of 30 Hz, in the 2:1 interlaced scanning display system of the current television. It was also reported that, in case of opening and closing both eyes alternately, the limit frequency not sensing the flickering (CFF: critical flicker frequency) was about 55 Hz and that the field frequency needed to be at least 110 Hz in consideration of the flickering.
Thus, such conventional apparatus is associated with a drawback of requiring a display device capable of high-speed display, for the transmissive display device 604.
The object of the present invention is to provide a stereoscopic image display apparatus allowing to observe a satisfactory stereoscopic image, even with a display device with a low display speed (low frame frequency), by separating the left and right parallax images uniformly over the entire image area at the observing position of a predetermined height, and with the observation area widened in the vertical direction.
The above-mentioned object can be attained, according to an aspect of the present invention, by a stereoscopic image display apparatus comprising:
light source means for emitting light from plural apertures;
an optical element array consisting of an array of optical elements having different optical functions in the horizontal and vertical directions for giving directionality to the light from the apertures; and
a transmissive display device for displaying a stripe image formed by alternately arranging, in a predetermined order, right stripe pixels and left stripe pixels obtained by dividing each of a parallax image for the right eye and a parallax image for the left eye in the vertical direction;
wherein the plural apertures are provided, for each stripe pixel, respectively corresponding to the optical elements constituting the optical element array and are adapted to direct all the light, transmitted by the left or right stripe pixel, to the predetermined respective area.
The plural apertures are preferably formed in a checkered pattern (in other words, rectangular patterns showing two colors alternately).
The pitch in the vertical direction of the apertures corresponding to the vertically adjacent stripe pixels is larger than the vertical pitch of the stripe pixels, and the width in the vertical direction of the apertures is smaller than the vertical width of the stripe pixel.
The optical element is preferably formed as a cylindrical lens having an optical power in the horizontal direction, and the optical element array is preferably composed of a horizontal array of such cylindrical lenses.
The pitch in the horizontal direction of the cylindrical lens is smaller than the pitch of the laterally adjacent ones of the apertures in the above-mentioned checkered pattern.
There is further provided means for controlling the apertures with a predetermined signal.
The control means is adapted to form the plural apertures in a predetermined area in the light source means and to cause light emission in all other areas.
The light source means is a light-emitting display device, and the control means is adapted to control the light-emitting display device.
Otherwise the light source means includes a surface illuminant and a transmissive spatial light-modulating device, and the control means is adapted to control the spatial light-modulating device.
A first stripe image, combined by alternately arranging odd one among the right stripe pixels obtained by dividing the parallax image for the right eye and even one among the left stripe pixels obtained by dividing the parallax image for the left eye, and a second stripe image, combined by alternately arranging odd ones among the left stripe pixels and even ones among the right stripe pixels, are alternately displayed over the entire area of the display device or in a predetermined area thereof.
The display is made, in switching the two stripe images to be displayed on the display device and the plural apertures formed on the light-emitting face of the light source means in raster scanning, by switching for each scanning line or for each pixel on the corresponding scanning line.
Between the light source means and the display device, there is provided a second mask having plural lateral stripe-shaped apertures respectively corresponding to the stripe pixels constituting the stripe image.
The pitch in the vertical direction of the apertures of the second mask, corresponding to the vertically adjacent stripe pixels, is larger than the vertical pitch of the stripe pixels, but is smaller than the vertical pitch of the apertures of the light source means, and the width in the vertical direction of the apertures of the second mask is smaller than the vertical width of the stripe pixels.
The stripe pixels constituting the stripe image are displayed in a scanning line of the display device.
The stripe images are displayed in 2:1 interlaced display on the display device, and a stripe image consisting solely of the right stripe pixels and another stripe image consisting solely of the left stripe pixels are displayed in respective fields.
The optical element array is adapted to convert the light beams from the apertures of the light source means into substantially parallel light beams in the horizontal cross section and into converged light beams which is substantially converged on the display device in the vertical cross section.
The optical element array is provided with a vertical cylindrical lens array, consisting of an array in the horizontal direction of a plurality of vertically elongated cylindrical lenses, and a horizontal cylindrical lens array, consisting of an array in the vertical direction of a plurality of horizontally elongated cylindrical lenses.
The pitch VL in the vertical direction of the horizontal cylindrical lens array, the pitch Vd in the vertical direction of the stripe pixels displayed on the display device, the pitch Vm of the apertures in the vertical direction, the distance L1 between the display device and the horizontal cylindrical lens array, the distance L2 between the horizontal cylindrical lens array and the light source means, and the focal length fv in the vertical cross section of the horizontal cylindrical lenses constituting the horizontal cylindrical lens array satisfy the following relations:
Vd:Vm=L1:L2
Vd:VL=(L1+L2)/2:L2
1/fv=1/L1+1/L2.
A predetermined distance from the display device to the observer stands in the following relation with the above-mentioned parameters:
Vd:Vm=L:(L+L1+L2).
The optical element array includes a toric lens array consisting of a two-dimensional array of toric lenses having different focal lengths in the vertical and horizontal directions.
The optical element array is provided with a vertical cylindrical lens array, consisting of an array in the horizontal direction of a plurality of vertically elongated cylindrical lenses, and a horizontal cylindrical lens array, consisting of an array in the vertical direction of a plurality of horizontally elongated cylindrical lenses.
The pitch VL in the vertical direction of the toric lens array, the pitch Vd in the vertical direction of the stripe pixels displayed on the display device, the pitch Vm of the apertures in the vertical direction, the distance L1 between the display device and the horizontal cylindrical lens array, the distance L2 between the toric lens array and the light source means, and the focal length fv in the vertical cross section of the toric lenses constituting the toric lens array satisfy the following relations:
Vd:Vm=L1:L2
Vd:VL=(L1+L2)/2:L2
1/fv=1/L1+1/L2.
A predetermined distance from the display device to the observer stands in the following relation with the above-mentioned parameters:
Vd:Vm=L:(L+L1+L2).
The pitch P3X of the optical element array in the horizontal direction, the pitch P0X of the apertures of the light source means, the distance L0 between the optical element array and the predetermined observer position, and the distance d1 between the optical element array and the light source means satisfy the following relation:
L0:(L0+d1)=P3X:P9X
The above-mentioned object can be attained, according to another aspect of the present invention, by a stereoscopic image display apparatus comprising:
light source means for emitting light from plural apertures;
an optical element array consisting of an array of optical elements having different optical functions in the horizontal and vertical directions for giving directivity to the light from the apertures; and
a transmissive display device for displaying a stripe image formed by alternately arranging, in a predetermined order, right stripe pixels and left stripe pixels obtained by dividing each of a parallax image for the right eye and a parallax image for the left eye in the lateral direction;
wherein the plural apertures are provided, for each stripe pixel, respectively corresponding to the optical elements constituting the optical element array and are adapted to direct all the light, transmitted by the left or right stripe pixel, to the predetermined respective area.
The optical element is preferably formed as a cylindrical lens having an optical power in the horizontal direction, and the optical element array is preferably composed of a horizontal array of such cylindrical lenses.
The centers of the apertures corresponding to the right and left stripe pixels are shifted in mutually opposite directions, with respect to the optical axis of the cylindrical lenses respectively corresponding to the stripe pixels.
The width I of the right or left stripe pixel, the distance C from the display device to the light-condensed area, the distance E between the centers of the light-condensed areas, and the distance t from the principal plane of the cylindrical lens at the side of the display device to the display surface of the display device satisfy the following relation:
t=IC/(E/2xe2x88x92I)
There is further provided means for controlling the apertures with a predetermined signal.
The control means is adapted to form the plural apertures in a predetermined area in the light source means and to cause light emission in all other areas.
The light source means is a light-emitting display device, and the control means is adapted to control the light-emitting display device.
Otherwise the light source means includes a surface illuminant and a transmissive spatial light-modulating device, and the control means is adapted to control the spatial light-modulating device.
A first stripe image, combined by alternately arranging odd one among the right stripe pixels obtained by dividing the parallax image for the right eye and even one among the left stripe pixels obtained by dividing the parallax image for the left eye, and a second stripe image, combined by alternately arranging odd ones among the left stripe pixels and even ones among the right stripe pixels, are alternately displayed over the entire area of the display device or in a predetermined area thereof.
The display is made, in switching the two stripe images to be displayed on the display device and the plural apertures formed on the light-emitting face of the light source means in raster scanning, by switching for each scanning line or for each pixel on the corresponding scanning line.
The present invention will become fully apparent from the following detailed description of embodiments.